Control system for an automatic dishwasher



April 22, 1969 D. S.'CUSHING 3,439,687

CONTROL SYSTEM FOR AN AUTOMATIC DISHWASHER F iled March 24, 1967 Sheetof 5' IO 58 f l n n [l I I I I l H I I l l l L J n, u u I n [l [1 H H [1u u u u u lei-T W 16 INVENTOR DONALD s. cusume BY Z V 2 ms ATTORNEY p1969 D. s. CUSHING 3,439,687

CONTROL SYSTEM FOR AN AUTOMATIC DISHWASHER Filed March'24; 1967 Sheet 3of 5 INVENTOR. DONALD s. cusH\NG BY 5 Z mTTORNEY U.s. Cl. 134-57 UnitedStates Patent ABSTRACT OF THE DISCLOSURE A system employing a pressuresensitive fill switch to de-energize a water valve and energize a timermotor and motor-driven pump. Drain solenoid on pump is con trolled bytimer switch. Flood switch ameliorates malfunction of either water valveor fill switch by de-energizing water valve and allowing energization ofdrain solenoid.

Background of the invention This invention relates generally toautomatic dishwashers and, more specifically, to an improved andsimplified control system for an automatic dishwasher.

The operation of a typical automatic dishwasher for use in the homeinvolves several separate fills or charges of water, agitation orrecirculation of each charge of water within the wash chamber toeffectuate a wash or rinse action therein, and drainage of each charge.This provides, generally, one or more pro-rinses, a wash, and one ormore post-rinses. The last post-rinse is normally followed by a dryingperiod wherein the dishes are heated by an electrical heating element tofacilitate their drying. Additional rinses or washers may be added tothe fore going typical operational cycle.

Of course, control means must be provided to sequentially energize andde-energize the various components of the dishwasher to carry out thecycle. Usually, a sequence control means having a timer motor andseveral camoperated switches is provided with each switch controllingone of the components. Although such control means has proven successfuland is in general use today it is a relatively expensive component ofthe dishwasher, du in part to the large number of cams and switchesinvolved. Additionally, of course, the greater number of switches andcams which are involved increases the complexity of the device and thusincreases the likelihood of need for service.

Th amount of water in each charge admitted to the wash chamber must bemaintained within certain limits to assure, on the one hand, thatadequate water is present to effectuate suitable wash or rinse actionand, on the other hand, to avoid overflow or flooding which may resultif an excessive amount of water is admitted. Most dishwashersmanufactured today provide a timed fill. That is, the sequence controlmeans maintains the water valve open for a predetermined length of timewhich is calculated to provide a given amount of water within theaforementioned limits. This requires a relatively accurate, and thusexpensive, timer motor. Similarly, the draining of the wash chamber isgenerally time controlled which requires an accurate timer motor toassure complete drainage or, in the alternative, requires a margin ofsafety in the form of excessive drain time which creates undesirablenoise as the drain pump continues to run after the wash chamber isdrained and which also tends to elongate the time of the overalloperational cycle of the dishwasher.

As will become evident as this description proceeds, the presentinvention provides an improved control system for an automaticdishwasher which is greatly simplified in "ice comparison to heretoforeavailable controls but which provides all the functions of the morecomplex systems. Moreover, the control system of the present inventionallows use of a less accurate timer motor since fill and drainage of thewash chamber are not subject to the timed accuracy of the sequencecontrol means. Additionally, overflow protection is provided.

Summary of the invention This invention is related to an automaticdishwasher having a wash chamber, a motor-driven pump having a housing,an ele'ctricallyoperated valve to control the flow from the pump andhaving a wash position and a drain position, and anelectrically-operated means to admit water to the Wash chamber.Specifically, this invention provides an improved control systemcomprising a pressure sensitive fill switch having first and secondoperative positions and located to sense the pressure within the pumphousing. A sequence control means including a timer motor and at leastone switch having at least one closed position and operated inpredetermined sequence by the timer motor is also provided. The means toadmit water is electrically connected to the fill switch to be energizedwhenever the fill switch is in its first operative position. The timermotor and the motor-driven pump are electrically connected to the fillswitch to be energized whenever the fill switch is in its secondoperative position. The electrically-operated valve is connected to thefill "switch and to the switch in the sequence control means whereby theelectrically-operated valve is moved toward its drain position wheneverthe fill switch is in its second operative position and the switch inthe sequence control means is in its closed position.

In a specific embodiment of the present invention, a level sensitiveflood switch is positioned to operate as the liquid level within thewash chamber exceeds a predetermined height. The flood switch is inelectrical series circuit with the means to admit water to override thefill switch and de-energize the means to admit water whenever the liquidlevel exceeds the predetermined height.

Brief description of the drawings While the specification concludes withclaims particularly pointing out and distinctly claiming the subjectmatter which is regarded as the invention, it is believed that theinvention will be better understood from the following description ofthe preferred embodiments taken in connection with the accompanyingdrawings, in which:

FIGURE 1 is an elevational view, partially cut away to show details, ofan automatic dishwasher employing the present invention;

FIGURE 2 is an enlarged detail view of a pump and a valve employed inthe dishwasher of FIGURE 1;

FIGURE 3 is a fragmentary view of the pump of FIG- ure 2 viewed from theside opposite that of FIGURE 2;

FIGURE 4 is a schematic representation of the electrical circuitry ofthe control system of the present invention;

FIGURE 5 is a schematic representation of the action of the timercontrolled switches in the circuitry of FIG- URE 4; and

FIGURE 6 is a schematic representation similar to that of FIGURE 4 butshowing a modification thereof.

Description of the preferred embodiments Referring now to the drawings,and particularly to FIGURE 1 thereof, there is illustrated an automaticdishwasher -10 having an outer cabinet 11 defining therein a washchamber 12. Disposed within wash chamber 12 are dish-supporting racks 13and 14 which are adapted to receive and support dishes or other articlesto be washed within wash chamber 12. A door 15 is provided in one wallof cabinet 11, pivotal about a hinge means 16, a to provide access towash chamber 12. When door is pivoted downwardly, rack 13 can be atleast partially withdrawn from wash chamber 12 by means of a slide androller system 17 provided at each side of rack 13 and slidablysupporting rack 13 from the inner wall of cabinet 11. Similarly, rack 14can be at least partially withdrawn from wash chamber 12 by means of aroller 18 which rides upon a track 19 provided at each side of cabinet11.

The lower extremity of wash chamber 12 is defined by a bottom wall 20which gradually slopes to a low point 21 near the center of thedishwasher. Disposed below the low point 21 is a sump 22 which may beformed integrally with the bottom wall 20 or which may be a separateelement secured thereto. Projecting upwardly from bottom wall 20 nearthe center of wash chamber 12 is a pedestal 23 which rotatably supportsa reaction-type spray device 24. Spray device 24 as a plurality oforifices 25 through which wash fluid is ejected to eflectuate a washaction upon articles supported by rack 13 and 14. At least one of theorifices 25 is directed such that the reaction force created by washfluid passing therethrough causes rotation of spray device 24 about asubstantially vertical axis.

Wash fluid is propelled into spray device 24 by a pump 26 which isdriven by an electric motor 27. Pump 26 and motor 27 are securedtogether to form a motor-pump assembly which is suitably supported frombottom wall 20. A flexible boot or conduit 28 interconnects sumps 22with the inlet of pump 26. Boot 28 is secured to sump 22 by means of aclamp 29 and is similarly secured to pump 26 by means of a clamp 30.

Referring now to FIGURES 2 and 3, it can be seen that pump 26 has ahousing 31 defining an inlet 32 which receives fluid from boot 28.Disposed within housing 31 is an impeller (not shown) mounted forrotation to pump fluid through housing 31 and driven by motor 27. Afirst outlet 33 interconnects pump 26 with spray device 24 while asecond outlet 34 interconnects pump 26 with a normal household sewersystem (not shown). Referring again briefly to FIGURE 1, it can be seenthat outlet 33 is connected to a flexible conduit 35 by means of aclamp36. Conduit 35 extends up through pedestal 23 to a fitting 37 upon whichspray device 24 is rotatably mounted, it being understood that fitting37 is secured to pedestal 23. Referring again to FIGURES 2 and 3, water,or other liquid, entering pump 26 through inlet 32 will be pumped eitherinto spray device 24 through outlet 33 or discharged from dishwasher 10through outlet 34.

An outlet valve mechanism 38 is provided to selectively control throughwhich of the outlets 33 or 34 the fluid will egress from pump 26. Outletvalve mechanism 38 includes a frame 39 suitably secured to pump housing31. Frame 39 carries a solenoid 40 having electrical terminals 41 and 42and an armature 43. Armature 43 is adapted to be drawn into solenoid 40to the position illustrated in FIG. 3 when solenoid 40 is energized bythe presence of electrical energy across terminals 41 and 42. Armature43 has attached thereto a link 44 which extends out from armature 43 andthen laterally through a slot 45 in frame 39. Link 44 is provided with awasher 46 rigidly secured thereto to prevent link 44 from escaping fromslot 45. Link 44 also passes through a slot 47 in a plate 48. Plate 48is carried by arm 49 which is pivotally carried by pump housing 31 andextends into pump housing 31. Within pump housing 31, arm 49 has asubstantially 90 bend and supports within pump housing 31 valve elements50 and 51. Valve element 50 is adapted to seal off outlet 33, and thusdirect fluid from pump 26 out through outlet 34, when outlet valvemechanism 38 is in one condition of operation (shown in dotted lines inFIGURE 2). Valve element 51 is adapted to seal off outlet 34, and thusdirect fluid from pump 26 out through outlet 33, when valve mechanism 38is in the other condition of operation (also shown in dotted lines inFIGURE 2).

A spring 51a is secured at one end to frame 39 and at its other end toplate 48 to normally urge plate 48 to rotate in a direction wherebyvalve element 51 seals oif outlet 34. When solenoid 40 is energized, itovercomes the force of spring 51a to move valve element 50 towardsealing engagement with outlet 33. As can be seen from a review ofFIGURES 2 and 3, when armature 43 is fully drawn into solenoid 40, plate48 and arm 49 assume the positions shown in solid lines in FIGURES 2 and3. Thus, when solenoid 40 is energized, valve element 50 is moved onlypart way toward sealing engagement with outlet 33; however, when pump 26is operating and fluid is passing therethrough, the pressure of thefluid will move arm 49 and valve element 50 to the position whereinelement 50 seals off outlet 33. The fluid pressure will maintain valveelement 50 in sealing relationship with outlet 33 until substantiallyall of the fluid has been pumped out through outlet 34 whereupon thepressure within housing 31 will drop and spring 51a will move arm 49 tothe position wherein outlet 33 is opened and outlet 34 is closed. Slot47 is elongated to allow arm 49 and plate 48 to pivot in response to thefluid pressure to the position wherein valve element 50 seals off outlet33 even though link 44 remains stationary.

The outlet valve mechanism 38, including arm 49 and valve elements 50and 51 is described in greater detail, along with other refinementsthereof, in application Ser. No. 549,675, filed May 12, 1966 by ThomasE. Jenkins, now Patent No. 3,367,368, issued Feb. 6, 1968, and assignedto the General Electric Company, assignee of the present invention. Thisapplication does not claim as new the outlet valve mechanism per se.

An electrical heating means 52 is supported in spaced relationship frombottom wall 20 and may be employed to heat the wash fluid in washchamber 12, although not so adapted in this application, and tofacilitate drying of articles supported by racks 13 and 14 uponcompletion of the wash and rinse operations. Means, in the form of anelectrically-operated valve 53, are provided to control the admission ofwater, or other fluids, to wash chamber 12. Valve 53 is connected at oneside to a conduit 54 which communicates with the normal householdplumbing system and, at the other side, is connected to a conduit 55which communicates with wash chamber 12 through an inlet funnel 56. Asequence control means 57, having a manually operable knob 58, isconveniently positioned on door 15. Sequence control means 57 isdisposed within door 15 and knob 58 projects out through the frontwallthereof to be conveniently manipulated by the operator of thedishwasher 10.

Referring now to FIGURE 4, the control system of the present inventionis illustrated in schematic form. As can be seen, sequence control means57 includes a timer motor 59 which, in a conventional sequence controlmeans would comprise a synchronous electric motor due to its accuracy,but in the present application, for reasons to become evident as thedescription proceeds, may involve a less ac curate electric motor. Timermotor "59 drives, through direct mechanical linkage, cams 60 and 61. Cam60 controls the operation of switch 62 while cam 61 controls theoperation of switch 63 in a manner well known in the appliance controlart. A pressure sensitive fill switch 64 is electrically connected toswitch 62 and valve 53. As can be seen in FIGURE l, fill switch 64 isphysically located to sense the pressure within the housing of pump 26.Fill switch 64 is a single pole double throw switch normally biasedtoward terminal 65 and is moved to terminal 66 as the pressure withinpump housing exceeds some predetermined value. It should be realizedthat the pressure sensed by fill switch 64 may be a static pressurecreated by a predetermined level of fluid filling the housing 31 of pump26, bottom 28, sump 22 and a portion of wash chamber 12 or it may bepressure created by operation of the impeller within pump 26 even thoughthe static level of fluid has decreased below that necessary to operatethe switch.

A level sensitive flood switch 67 is electrically connected to valve 53and heating means 52. Again referring briefly to FIGURE 1, it can beseen that flood switch 67 is physically positioned ideally within washchamber 12 to operate as the liquid level within wash chamber 12 exceedsa predetermined height. Flood switch 67 is biased to be normally closedagainst terminal 68, as illustrated in FIGURE 4, and closes againstterminal 69 as the liquid level within wash chamber 12 reaches, orexceeds, a predetermined height. This predetermined height is at thehighest allowable level which will avoid leakage of wash fluid from washchamber 12 through any vents or other openings which may be provided incabinet 11 or door 15.

Since the electrical connections among the various components of thecontrol system schematically represented in FIGURE 4 can be bestappreciated from a study of FIGURE 4, a detailed element by elementverbal description of the connections will not be given here.

A description of the operation of the control system of FIGURE 4 willnow be given as it relates to a complete operational cycle of dishwasher10. Power lines L and L are connected across a conventional source of110 volt, 6O cycle AC power. A master switch 70 is adapted to be closedas the latching means (not shown) for door 15 is operated to secure door15 in the closed position. Thus, switch 70 serves to deenergize thecontrol system at any time door 15 is not secured in its closed positointo prevent the inadvertent escape of wash fluid from wash chamber 12.Once door 15 has been secured in the closed position, knob 58 ismanipulated to initiate operation of dishwasher 10 by rotation thereof afew degrees which rotates cam 60 to close switch 62. As switch 62 isclosed, valve 53 is energized to begin the admission of water to thewash chamber 12 since fill switch 64 is closed against terminal 65 dueto the absence of water pressure in pump 26 and flood switch 67 isclosed against terminal 68 due to the absence of sufliciently highliquid level within wash chamber 12. Valve 53 is energized by the flowof current therethrough which also passes through heating means 52.Heating means 52 may be of the con ventional electrical resistance typewhich is of low impedance. A heating means of the size illustrated inFIGURE 1 and normally used in dishwasher of the type shown, would havean impedance of 15 to ohms. The control system would remain in thiscondition, i.e., valve 53 in the open position allowing water to enterwash chamber 12, until the level of water reached a height wherein thepressure at switch 64 exceeded the predetermined level, whichcorresponds to a normal charge of water. At this point, switch 64 wouldopen from terminal 65 and close on terminal 66 thus de-energizing valve53 and terminating the admission of water to wash chamber 12.

As switch 64 closes against terminal 66, .timer motor 59 is energizedthrough flood switch 67 and heating means 52 to drive cams '60 and 61.Motor 27 is also energized, in parallel with timer motor 59, to drivepump 26 and propel the fluid up through spray device 24 to eflectuatethe first rinse of the articles contained therein. As the fluid ispumped up through spray device 24, the static level decreases; however,operation of pump 26 builds up a sustaining pressure on fill switch 64to keep it closed on terminal 66 even though the static level decreasesbelow that necessary to keep switch 64 closed on terminal 66.

Referring now to FIGURE 5, the action of switches 62 and 63, due to theconfigurations of earns 60 and 61 respectively, is illustrated. Thus, itcan be seen after a few minutes, specifically the duration of the firstpre-rinse, cam 61 closes switch 63 on terminal 71. This energizessolenoid 40 to move valve element 50 toward sealing engagement withoutlet 33. As discussed above, the fluid pressure within the housing 31moves valve element into complete sealing engagement with outlet 33 andopens outlet 34. Thus, pump 26 will eflectuate draining of the fluidfrom the dishwasher. This condition will obtain until substantially allthe fluid has been drained from the dishwasher at which time fill switch64 will again close on terminal 65 thus de-energizing solenoid 40, timermotor 59 and motor 27. As motor 27 is de-energized, spring 51a willrotate arm 49 to bring valve element 51 into sealing engagement withoutlet 34 and will open outlet 33.

It should be noted at this time that because switch 64 senses thepressure within pump housing 31, it remains closed on terminal 66 untilsubstantially all of the water has been pumped out through outlet 34even though the static pressure created by the level of water in bootI28 and sump 22 is less than that required to maintain switch 64 closedagainst terminal 66 under static conditions. Thus, solenoid 40 and motor27 remain energized until substantially all of the fluid has been pumpedfrom the dishwasher.

It should be noted that switch 63 need be maintained in its closedposition on terminal 71 for only a few seconds and may then be returnedto its ofl position. Once the fluid pressure has established valveelement 50 in sealing relationship with outlet 33, it is no longernecessary to maintain solenoid 40 energized. It is necessary tode-energize solenoid 40 so that spring 51a will be free to move valveelement 51 into sealing relationship with outlet 34 as soon as thepressure within pump 26 decreases as substantially all of the fluid ispumped out through outlet 34.

A review of FIGURE 5 will show that the foregoing described sequence ofevents may be repeated several times and, in the preferred form, wouldbe performed a total of five times. The first two times would providepre-rinses, the third time would provide an elongated wash whereindetergent is added to the water by means of a detergent dispenser (notshown), and the last two would provide post-rinses. Following the secondpostrinse, cam 61 is configurated to move switch 63 into contact withterminal 72 to thus apply the full voltage L L across heating means 52.Since fill switch 64 will close on terminal 65 as the water is drainedfrom pump housing 31, timer motor 59 will be energized by completion ofa circuit through terminal 72 of switch 63, terminal 68 of flood switch67 and the low impedance motor winding of motor 27. A shaded pole orinduction motor of suitable power to drive pump 26 has an impedance ofapproximately 2 ohms. Thus, sufiicient voltage will be dropped acrosstimer motor 59 to cause it to run. Since the current through timer motor59 is approximately 0.2 amp., the voltage across motor 27 isapproximately 0.4 volt. Thus motor 27 does not run during thiscondition. Valve 53 will not be energized even though fill switch 64 isclosed on terminal 65 and flood switch 67 is closed on terminal 68because the circuit through terminal 72 of switch 63 shunts valve 53.This condition exists for several minutes and comprises the dryingportion of the operational cycle with the heat generated by heatingmeans 52 serving to facilitate drying of the articles supported by racks13 and 14. Upon the termination of the predetermined length of time ofthe drying portion of the cycle, cam 60 opens switch 62 to de-energizethe entire control system. Cam 61 returns switch 63 to its olf positionduring manual turning of knob 58 at the beginning of a subsequent cycle.

Flood switch 67 remains closed on terminal 68 at all times during normaloperation of a dishwasher 10 and closes upon terminal 69 only duringthat abnormal condition when excessive amounts of water, or other fluid,is present in wash chamber 12. Such abnormal condition may occur in theevent that fill switch 64 fails to operate properly and continues tomaintain valve 53 in its open position even though the required chargeof water has been admitted to the dishwasher.

When an excessive amount of water operates flood switch 67 to closeagainst terminal 69, due to a malfunction of switch 64, it can be seenthat timer motor 59 and solenoid 40 will be energized along with motor27, with current flowing through switch 64, valve 53, timer motor 59,and then through solenoid 40 and heater 52 in parallel with motor 27.Although a circuit is established through valve 53, the impedance oftimer motor 59 is relatively high (approximately 800 ohms compared to600 ohms for valve 53) leaving an insuflicient voltage drop across valve53 to cause opening thereof. When such a situation exists, the operatorof the dishwasher will recognize the face that a problem exists due tothe fact that the cycle will not be completed. The dishwasher may beleft in this condition until a serviceman arrives to repair themalfunctioning switch 64.

In the event that an excessive amount of water gains admission to washchamber 12 even though switch 64 is operating properly, then switch 64would be closed against terminal 66 and flood switch 67 would be closedagainst terminal 69. In this condition, timer motor 59 would not beenergized; however, solenoid 40 would be energized through switch 67 andheater 52 while motor 27 would be energized also thus placing thecontrol system in the drain position. Such a situation could occur ifvalve 53 experienced a mechanical malfunction wherein it was stuck inthe open position and remained in that position even though theelectrical energy thereof was terminated. Because the capacity of pump26 greatly exceeds that of valve 53, escape of fluid from dishwasherwould be prevented as long as solenoid 40 and motor 27 remainedenergized. Since most dishwashers are provided with a manually operablevalve in series with valve 53, the operator of the dishwasher couldclose the manual valve to shut off the supply of water to the dishwasheruntil a Serviceman arrived to correct the malfunction.

Referring now to FIGURE 6, a modification of the control system ofFIGURE 4 is illustrated and involves, primarily, repositioningelectrically of the flood switch to a location adjacent master switch70. In FIGURE 6, the flood switch is given the numeral 67a and itscontacts are given the numerals 68a and 69a. Similarly, the fill switchis given a numeral 64a and its terminals are given the numerals 65a and66a. The remaining elements of the control system carry the samenumerals as those in FIGURE 4 since they may be substantially identicalthereto. The system of FIGURE 6 operates substantially the same as thesystem of FIGURE 4 as long as the liquid level within wash chamber 12does not reach a height sufficient to cause flood switch 67a to closeupon terminal 69a. Flood switch 67a normally remains closed on theterminal 68a. Fill switch 64a remains closed on terminal 65a, untilswitch 64a senses a pressure in pump 26 of a predetermined levelwhereupon switch 64a closes on terminal 66a. When switch 64a closes onterminal 66a, it can be seen that timer motor 59 will be energizedthrough heating means 52 and motor 27 will also be energized withsolenoid 49 remaining de-energized until switch 63 is closed uponterminal 71 by cam 61 as in the system of FIGURE 4. When switch 63closes on terminal 71, solenoid 40 will effectuate draining of the fluidfrom the dishwasher and, as all the fluid drains therefrom, switch 64awill again close on terminal 65a to initiate a repetition of thesequence of events.

The drying portion of the cycle finds flood switch 67a closed onterminal 68a and fill switch 64a closed on terminal 65a. Heating means52 is energized through terminal 72 of switch 63. Timer motor 59 isenergized through terminal 72 of switch 63 and then in parallel toheater 52 through the low impedance winding of motor 27. Switch 63shunts valve 53 to prevent admission of water to wash chamber 12.

The operation of the flood switch 671; is such that when it closes onterminal 69a, valve 53 is de-energized, despite the setting of switch64a, and timer motor 59 and motor 27 are energized. Thus, in the eventof a malfunction of fill switch 64a, valve 53 will de-energized toterminate admission of water to wash chamber 12 and no additional watermay be admitted until the level within wash chamber 12 has decreased tothe extent that flood switch 67a closes on terminal 68a. The level willbe lowered through the normal operation of sequence control means 57wherein cam 61 will cause switch 63 to eventually close on terminal 71thus energizing solenoid 40 to drain wash chamber 12. The arrangement ofFIG- URE 6 may prove to be advantageous over that of FIG- URE 4 in theevent that a trickle leak in valve 53 is established. This is a sort ofleak which may occur if a small grain of sand lodges between the valveand the valve seat thus allowing a very slight trickle of water to passthrough valve 53 even though it is de-energized. If this occurs, andmaster switch 70 is closed, flood switch 67a will energize the system,as described above, even though sequence control means 57 has not beenmanually energized by knob 58. Such a situation could occur, forexample, when a home owner leaves on vacation for several weeks duringwhich period of time the trickle of water may accumulate suflicientwater within wash chamber 12 to create an overflow condition. The homeowner need only secure door 15 to close switch 70 to create a pump outor drainage of dishwasher 10 as the accumulation of water thereinreaches the overflow stage.

Thus, the aforedescribed invention provides an improved control systemfor an automatic dishwasher which is greatly simplified due to the factthat only two timer operated switches are involved. A positive measuredfill of each charge of dishwasher is provided, flood protection isprovided and the main motor, such as motor 27, is deenergized as soon assubstantially all the water has been drained from the dishwasher thusreducing the amount of noise generated by the dishwasher during anoperational cycle thereof. Moreover, the positive measured fill and theemployment of a pressure sensitive fill switch to con rol drainingallows the use of a less accurate, and thus less expensive, timer m'otorsince the only operation which require accurate timing in conventionalcontrol systems, fill and drain, are not subject, in the present controlsystem, to the accuracy of the sequence control means.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. In an automatic dishwasher having a wash chamber, a pump having ahousing, a pump motor to drive said pump, an electrically-operatedoutlet valve to control the flow from said pump and having a drainposition, and an electrically-operated water valve to admit water tosaid wash chamber, a control system comprising:

(a) a pressure sensitive fill switch having first and second operativepositions and located to sense the pressure within said pump housing,

(b) said fill switch being held in said second position when thepressure within said pump housing exceeds a predetermined level,

(c) a sequence control means including a timer motor and at least oneswitch having at least one closed position and operated in predeterminedsequence by said timer motor,

(d) said water valve being electrically connected to said fill switch tobe energized when said fill switch is in said first operative position,

(e) said timer motor and said pump motor being electrically connected tosaid fill switch to be energized when said fill switch is in said secondoperative position,

(f) said outlet valve being electrically connected to said fill switchand to said switch in said sequence control means whereby said outletvalve is moved toward said drain position when said fill switch is insaid second operative position and said switch in said sequence controlmeans is in said closed position.

2. The invention of claim 1 further comprising a level sensitive floodswitch positioned to operate as the liquid level within said washchamber exceeds a predetermined height, said flood switch being inelectrical series circuit with said water valve to over-ride said fillswitch and deenergize said water valve whenever said liquid levelexceeds said predetermined height.

3. The invention of claim 1 further comprising an electrical heatingelement to facilitate drying of articles within said wash chamber andsaid switch in said sequence control means has a second closed positionto energize said heating element during a predetermined timed interval.

4. The invention of claim 1 further comprising a level sensitive floodswitch having first and second operative positions and located to moveto said second operative position as the liquid level within said washchamber exceeds a predetermined height, said flood switch when in saidfirst operative position allowing energization of said water valve butwhen in said second operative position energizing said sequence controlmeans and energizing said pump motor while preventing energization ofsaid water valve.

5. In an automatic dishwasher having a wash chamber, a pump having ahousing, a pump motor to drive said pump, an electrically-operatedoutlet valve to control the flow from said pump and having a drainposition, and an electrically-operated water valve to admit water tosaid wash chamber, a control system comprising:

(a) a sequence control means having a timer motor and at least one timerswitch controlled by said timer motor,

(b) a fill switch having first and second terminals,

() said fill switch being normally closed on said first terminal andbeing sensitive to the pressure within said pump housing to open saidfill switch from said first terminal and close it on said secondterminal when said pressure exceeds a predetermined level,

(d) said first terminal being electrically connected to said watervalve,

(e) said second terminal being electrically connected to said timerm'otor, said outlet valve, and said pump motor,

(f) said timer switch being electrically connected to said outlet valvein electrical series circuit with said second terminal whereby saidoutlet valve is energized and moved toward said drain position when saidtimer switch is closed and said fill switch is closed on said secondterminal.

6. The invention 'of claim 5 wherein said fill switch deenergizes saidoutlet valve, said timer motor and said pump motor and energizes saidwater valve as the pressure within said pump housing decreasessufficiently to open said fill switch from said second terminal andclose it on said first terminal.

7. The invention of claim 5 further comprising a fi'ood switch having atleast one terminal electrically connected to said outlet valve inelectrical parallel circuit with said timer switch whereby said outletvalve is energized and moved toward said drain position when said floodswitch is closed on said 'one terminal even though said timer switch maybe open, said flood switch being sensitive to the level of liquid withinsaid wash chamber to close on said one terminal when said level exceedsa predetermined height.

8. The invention of claim 7 wherein said flood switch has a secondterminal electrically connected to said water valve in electrical seriescircuit with said fill switch whereby said water valve is de-energizedas said flood switch opens said second terminal and closes on said oneterminal.

9. The invention of claim 5 further comprising a flood switch having afirst terminal and a second terminal, said second terminal beingconnected in electrical series circuit with said fill switch and saidfirst terminal being electrically connected to said timer motor, saidpump motor and said timer switch, said flood switch being positioned tosense when the level of liquid within said wash chamber exceeds apredetermined level, said flood switch being adapted to open from saidsecond terminal and close on said first terminal as said level exceedssaid predetermined height whereby said water valve is de-energized andsaid timer motor and said pump are energized and said 'outlet valve willbecome energized upon closing of said timer switch.

References Cited UNITED STATES PATENTS 3,078,858 2/1963 Jacobs et a1.3,124,145 3/1964 Egle. 3,334,651 8/ 1967 Clearman.

DANIEL BLUM, Primary Examiner.

Us. 01. X.R. 1o3 s7, 97

